An elusive ancestry of Neogastropoda: a potential of Maturifusidae, Pseudotritoniidae, and Purpurinidae as the stem groups

Notwithstanding considerable efforts and new data on gastropod evolution collected in the recent decades, the origin of Neogastropoda remains still elusive. In this contribution we compare and ­discuss members of three extinct families previously proposed as possible neogastropod stem groups, i.e., Maturifusidae Gründel, 2001, Pseudotritoniidae Golikov & Starobogatov, 1987, and Purpurinidae Zittel, 1895. Their morphological characteristics, especially the differences in protoconch morphology, strongly suggest that they should all be considered as separate clades. The taxonomic status and the composition of each family is here reviewed and accordingly revised. Angularia kittli n. sp. is introduced from the Carnian (Late Triassic) of the St. Cassian Formation (Italy). It differs from its congeners in having a more pronounced axial ornamentation, which makes it similar to Fossacerithium Gerasimov, 1992 from the Jurassic. However, the protoconch of the new species is unknown and therefore its taxonomic position is tentative. An evolutionary lineage from the oldest known purpurinid species of genera Khetella Beisel, 1977 and Cretadmete Blagovetshenskiy & Shumilkin, 2006 to the recent tonnoids is proposed. We conclude that in the Jurassic, purpurinids were divided into two groups. One of them, represented by Khetella, could be considered as the ancestor of Tonnoidea, while the other, represented by Fossacerithium, can be interpreted as the ancestor of Neogastropoda. Maturifusidae most likely went extinct without direct descendants. The relation of Pseudotritoniidae to the neogastropod lineage remains uncertain.